Bouldering is a type of climbing that involves short ascents without a rope. Bouldering climbs are called “problems” because they are a relatively short series of moves that need to be solved. Boulder problems are often very acrobatic and quite physical: they might only be 5 moves long, but each move is a huge effort. For this reason, bouldering is often more physically demanding than roped climbing, so it’s not necessarily the best type of climbing for beginners.
Since there are no ropes in bouldering, every bouldering fall is a ground fall. Thick “bouldering pads” are used to soften the fall when climbing outdoors and indoor gyms cover the bouldering area with thick padding (N3C’s bouldering flooring system 13” thick and has 3 different densities of foam). Even with the padded floor, however, you need to pay attention to how you fall while bouldering and always have a spotter to redirect your fall in case you fall out of control.
In the US, boulder problems use the “V scale” to rate difficulty. The easiest problems on this scale are rated V0 and the hardest (currently) are V16. Note that even a boulder problem rated V0 is pretty difficult. Every move will be about the same difficulty as the hardest move of a roped climb rated 5.9 (more about roped ratings here).